Japan PM cancels trip over megaquake.

Japan has - for the first time - issued a warning about an increased risk of a "major earthquake" striking in the near future.

The advisory was issued on Thursday night local time, telling people to be alert but not to evacuate. It also stressed that the warning did not mean a large earthquake was imminent, but that the probability was higher than usual.

It came hours after a 7.1 magnitude earthquake occurred off the southern island of Kyushu, which reportedly caused no major damage.